Complex composite article having improved impact resistance

ABSTRACT

The present invention provides an improved, complex composite article of manufacture which comprises a network of high strength fibers having a tensile modulus of at least about 160 grams/denier and a tenacity of at least about 7 g/denier. An elastomeric material substantially coats each of the individual fibers, and has a tensile modulus of less than about 6,000 psi, measured at 25° C. The coated fibers are provided with at least one additional rigid layer on a major surface of the coated fibers to produce a rigid complex composite. Composites of this construction have improved resistance to environmental hazards, improved impact resistance, and are unexpectedly effective as ballistic resistant articles such as armor plate or helmets.

This is a continuation-in-part of Ser. No. 06 707,010 2-28-85, U.S. Pat.No. 4,613,535.

BACKGROUND OF THE INVENTION

Ballistic articles such as bulletproof vests, helmets, armor plate, andother military equipment, structural members of helicopters, aircraft,ships, and vehicle panels and briefcases containing high strength fibersare known. Fibers conventionally used include aramid fibers, fibers suchas poly(phenylenediamine terephthalamide), graphite fibers, ceramicfibers, nylon fibers, glass fibers and the like. For these applications,the fibers are ordinarily encapsulated or embedded in a rigid matrixmaterial and, in some instances, are joined with rigid facing layers toform complex composite structures.

U.S. Pat. Nos. 4,403,012 and 4,457,985 disclose ballistic-resistantcomposite articles comprised of networks of ultra-high molecular weightpolyethylene or polypropylene fibers in matrices composed of olefinpolymers and copolymers, unsaturated polyester resins, epoxy resins, andother resins curable below the melting point of the fiber. While suchcomposites provide effective ballistic resistance, A. L. Lastnik, etal.; "The Effect of Resin Concentration and Laminating Pressures onKEVLAR® Fabric Bonded with Modified Phenolic Resin", Technical ReportNATICK/TR-84/030, June 8, 1984, have disclosed that an interstitialresin, which encapsulates and bonds the fibers of a fabric, reduces theballistic resistance of the resultant composite article. Therefore, aneed exists to improve the structure of composites to effectivelyutilize the properties of the high strength fibers.

U.S. patent application Ser. No. 691,048, Harpell et al., filed Jan. 14,1985, and commonly assigned, discloses a simple composites comprisinghigh strength fibers embedded in an elastomeric matrix. Surprisingly,the simple composite structure exhibits outstanding ballistic protectionas compared to simple composites utilizing rigid matrices, the resultsof which are disclosed therein. Particularly effective are simplecomposites employing ultra-high molecular weight polyethylene andpolypropylene such as disclosed in U.S. Pat. No. 4,413,110. However, thesimple composites, because of the use of a low modulus elastomericmatrix, may not be suitable in some applications where, for example,rigidity, surface hardness, chemical resistance or heat resistance maybe very important.

We have discovered complex composite structures which do not compromisethe advantageous properties of a simple composite formed of fibers in alow modulus elastomeric matrix while providing the requisite rigidity,surface hardness, chemical resistance or heat resistance, etc., neededfor certain applications. Moreover, complex composite structures of thisinvention are unexpectedly superior to the simple composite in ballisticprotection (at equal weight).

BRIEF DESCRIPTION OF THE INVENTION

The present invention is directed to a complex composite article ofmanufacture having improved rigidity and, in many instances, improvedresistance to environmental hazards which comprises of high strengthfiber having a tensile modulus of at least about 160 grams/denier and atenacity of at least about 7 grams/denier in an elastomeric matrixmaterial having a tensile modulus of less than about 6,000 psi (measuredat 25° C.), in combination with at least one additional layer arrangedon a major surface of the fiber in the elastomeric matrix material toform a structurally rigid, complex composite article.

The present invention is also drawn to a complex composite article ofmanufacture having improved rigidity and, in many instances, improvedresistance to environmental hazards which comprises a network of highstrength fibers having a tensile modulus of at least about 160grams/denier and a tenacity of at least about 7 grams/denier in anelastomeric matrix material having a tensile modulus of less than about6,000 psi, (measured at 25° C.) in combination with at least oneadditional layer arranged on a major surface of the network in theelastomeric matrix material adjacent the initial impact side of thenetwork in the elastomeric matrix to form a structurally rigid, complexcomposite article capable of effectively absorbing the energy of aprojectile.

The present invention also provides a complex composite article ofmanufacture having improved rigidity and, in many instances, improvedresistance to environmental hazards which comprises a network of highstrength fibers having a tensile modulus of at least about 500grams/denier and a tenacity of at least about 15 grams/denier in anelastomeric matrix material having a tensile modulus of less than about6,000 psi, (measured at 25° C.) in combination with at least oneadditional layer arranged on a major surface of the network in theelastomeric matrix material adjacent the initial impact side of thenetwork in the elastomeric matrix is provided to form a structurallyrigid complex ballistic resistant composite article.

Compared to conventional impact-resistant structures, and in particularto ballistic resistant armor, composite article of the present inventioncan advantageously provide a selected level of impact protection whileemploying a reduced weight of protective material. Alternatively, thecomposite article of the present invention can provide increased impactprotection when the article has a weight equal to the weight of aconventionally constructed composite such as composite armor.

DETAILED DESCRIPTION OF THE INVENTION

For the purposes of the present invention, fiber is an elongate body thelength dimension of which is much greater than the transverse dimensionsof width and thickness. Accordingly, the term fiber includes monofilament fiber, ribbon, strip, and the like having regular or irregularcross-section.

Complex composite articles of the present invention include a fibernetwork comprising highly oriented ultra-high molecular weightpolyethylene fiber, highly oriented ultra-high molecular weightpolypropylene fiber, aramid fiber, polyvinyl alcohol fiber,polyacrylonitrile fiber or combinations thereof. U.S. Pat. No. 4,457,985generally discusses such oriented ultra high molecular weightpolyethylene and polypropylene fibers, the disclosure of which is herebyincorporated by reference to the extent not inconsistent herewith. Inthe case of polyethylene, suitable fibers are those highly orientatedfibers of weight average molecular weight of at least about 500,000,preferably at least about one million and more preferably between abouttwo million and about five million. Known as extended chain polyethylene(ECPE) fibers, such fibers may be grown from polyethylene solution asdescribed, for example, in U.S. Pat. Nos. 4,137,394 to Meihuzen et al.or 4,356,138 to Kavesh et al., or spun from a solution to form a gelstructure as described in German Off. No. 3,004,699, GB No. 2051667, andespecially as described in application Ser. No. 572,607 of Kavesh et al.(see EPA 64,167, published Nov. 10, 1982). As used herein, the termpolyethylene shall mean a predominantly linear polyethylene materialthat may contain minor amounts of chain branching or comonomers notexceeding 5 modifying units per 100 main chain carbon atoms, and thatmay also contain admixed therewith not more than about 25 wt % of one ormore polymeric additives such as alkene-1-polymers, in particular lowdensity polyethylene, polypropylene or polybutylene, copolymerscontaining mono-olefins as primary monomers, oxidized polyolefins, graftpolyolefin copolymers and polyoxymethylenes, or low molecular weightadditives such as anti-oxidants, lubricants, ultra-violet screeningagents, colorants and the like which are commonly incorporatedtherewith. Depending upon the fiberforming technique, the draw ratio andtemperatures, and other conditions, a variety of properties can beimparted to these fibers. The tenacity of the fibers is ordinarily atleast about 15 grams/denier, preferably at least about 20 grams/denier,more preferably at least about 25 grams/denier and most preferably atleast about 30 grams/denier. Similarly, the tensile modulus of thefibers, as measured by an Instron tensile testing machine, is ordinarilyat least about 300 grams/denier, preferably at least about 500grams/denier, more preferably at least about 1,000 grams/denier and mostpreferably at least about 1,500 grams/denier. These highest values fortensile modulus and tenacity are generally obtainable only by employingsolution spun or gel fiber processes. In addition, many ECPE fibers havemelting points higher than the melting point of the polymer from whichthey were formed. Thus, for example, whereas ultra-high molecular weightpolyethylenes of 500,000, one million and two million generally havemelting points in the bulk of 138° C., the ECPE fibers made of thesematerials have melting points 7°-13° C. higher. The increase in meltingpoint reflect a higher crystalline orientation of the fibers as comparedto the bulk polymer. Notwithstanding the contrary teachings in the priorart, improved ballistic resistant articles are formed when polyethylenefibers having a weight average molecular weight of at least about500,000, a modulus of at least about 500 and a tenacity of at leastabout 15 g/denier are employed. Cf. John V. E. Hansen and Roy C. Laiblein "Flexible Body Armor Materials," Fiber Frontiers ACS Conference, June10-12, 1974 (ballistically resistent high strength fibers must exhibithigh melting point and high resistance to cutting or shearing); Roy C.Laible, Ballistic Materials and Penetration Mechanics, 1980 (noting thatnylon and polyester may be limited in their ballistic effectiveness dueto the lower melting point); and "The Application of High Modulus Fibersto Ballistic Protection", R. C. Laible, et al., J. Macromel. Sci. Chem.,A7(1), pp. 295-322, 1973 (the importance of a high degree of heatresistance is again discussed).

In the case of polypropylene, highly oriented polypropylene fibers ofweight average molecular weight at least about 750,000, preferably atleast about one million and more preferably at least about two millionmay be used. Ultra high molecular weight polypropylene may be formedinto reasonably highly oriented fibers by the techniques prescribed inthe various references referred to above, and especially by thetechnique of U.S. Ser. No. 572,607, filed Jan. 20, 1984, both to Kaveshet al. and commonly assigned. Since polypropylene is a much lesscrystalline material than polyethylene and contains pendant methylgroups, tenacity values achievable with polypropylene are generallysubstantially lower than the corresponding values for polyethylene.Accordingly, a suitable tenacity is at least about 8 grams/denier, witha preferred tenacity being at least 11 grams/denier. The tensile modulusfor polypropylene is at least about 160 grams/denier, preferably atleast about 200 grams/denier. The melting point of the polypropylene isgenerally raised several degrees by the orientation process, such thatthe polypropylene fiber preferably has a main melting point of at leastabout 168° C., more preferably at least about 170° C. Employing fibershaving a weight average molecular weight of at least about 750,000coupled with the preferred ranges for the above-described parameters(modulus and tenacity) can provide advantageously improved performancein the final article especially in ballistic resistant articles,(notwithstanding the contrary teachings in the prior art). C. f. Laible,Ballistic Materials and Penetration Mechanics, supra, at p. 81 (nosuccessful treatment has been developed to bring the ballisticresistance of polypropylene up to levels predicated from the yarnstress-strain properties); and The relative effectiveness of NTISpublication AD-A018 958, "New Materials in Construction for ImprovedHelmets", A. L. Alesi et al. [wherein a multilayer highly orientedpolypropylene film material (without matrix), referred to as "XP", wasevaluated against an aramid fiber (with a phenolic/polyvinyl butyralresin matrix); the aramid system was judged to have the most promisingcombination of superior performance and a minimum of problems for combathelmet development].

Aramid fiber is formed principally from the aromatic polyamide. Aromaticpolyamide fibers having a modulus of at least about 400 g/denier andtenacity of at least about 18 g/denier are useful for incorporation intocomposites of this invention. For example, poly(phenylenediamineterephalamide) fibers produced commercially by Dupont Corporation underthe trade name of Kevlar® 29 and 49 and having moderately high moduliand tenacity values are particularly useful in forming ballisticresistant composites. (Kevlar® 29 has 500 g/denier and 22 g/denier andKevlar® 49 has 1000 g/denier and 22 g/denier as values of modulus andtenacity, respectively).

In the case of polyvinyl alcohol (PV--OH), PV--OH fibers having a weightaverage molecular weight of at least about 500,000, preferably at leastabout 750,000, more preferably between about 1,000,000 and about4,000,000 and most preferably between about 1,500,000 and about2,500,000 may be employed in the present invention. Usable fibers shouldhave a modulus of at least about 160 g/denier, preferably at least about200 g/denier, more preferably at least about 300 g/denier, and atenacity of at least about 7 g/denier, preferably at least about 10g/denier and more preferably at least about 14 g/denier and mostpreferably at least about 17 g/denier. PV--OH fibers having a weightaverage molecular weight of at least about 500,000, a tenacity of atleast about 200 g/denier and a modulus of at least about 10 g/denier areparticularly useful in producing ballistic resistant composites. PV--OHfibers having such properties can be produced, for example, by theprocess disclosed in U.S. patent application Ser. No. 569,818, filedJan. 11, 1984, to Kwon et al. and commonly assigned.

In the case of polyacrylonitrile (PAN), PAN fiber of molecular weight ofat least about 400,000, and preferably at least 1,000,000 may beemployed. Particularly useful PAN fiber should have a tenacity of atleast about 10 g/denier and an energy to break of at least about 22joule/g. PAN fiber having a molecular weight of at least about 400,000,a tenacity of at least about 15-20 g/denier and an energy to break of atleast about 22 joule/g is most useful in producing ballistic resistantarticles; and such fibers are disclosed, for example, in U.S. Pat. No.4,535,027.

In the complex composite articles of our invention, the fibers may bearranged in networks having various configurations. For example, aplurality of fibers can be grouped together to form a twisted oruntwisted yarn. The fibers or yarn may be formed as a felt, knitted orwoven (plain, basket, satin and crow feet weaves, etc.) into a network,fabricated into non-woven fabric, arranged in parallel array, layered,or formed into a fabric by any of a variety of conventional techniques.Among these techniques, for ballistic resistance applications we preferto use those variations commonly employed in the preparation of aramidfabrics for ballistic-resistant articles. For example, the techniquesdescribed in U.S. Pat. No. 4,181,768 and in M. R. Silyquist et al. J.Macromol Sci. Chem., A7(1), pp. 203 et. seq. (1973) are particularlysuitable.

The fibers or fabrics may be premolded by subjecting them to heat andpressure. For ECPE fibers, molding temperatures range from about20°-155° C., preferably from about 80°-145° C., more preferably fromabout 100°-135° C., and more preferably from about 110°-130° C. Thepressure may range from about 10 psi to about 10,000. A pressure betweenabout 10 psi and about 100 psi, when combined with temperatures belowabout 100° C. for a period of time less than about 0.5 min., may be usedsimply to cause adjacent fibers to stick together. Pressures from about100 psi to about 10,000 psi, when coupled with temperatures in the rangeof about 150°-155° C. for a time of between about 1-5 min., may causethe fibers to deform and to compress together (generally in a film-likeshape). Pressures from about 100 psi to about 10,000 psi, when coupledwith temperatures in the range of about 150°-155° C. for a time ofbetween 1-5 min., may cause the film to become translucent ortransparent. For polypropylene fibers, the upper limitation of thetemperature range would be about 10°-20° C. higher than for ECPE fiber.

The fibers (premolded if desired) may be precoated with an elastomericmaterial comprising an elastomer prior to being arranged in a network asdescribed above. The elastomeric material has a tensile modulus,measured at about 23° C., of less than about 6,000 psi (41,400 kPa).Preferably, the tensile modulus of the elastomeric material is less thanabout 5,000 psi (34,500 kPa), and most preferably is less than about2,500 (17,250 kPa) to provide even more improved performance. The glasstransition temperature (T_(g)) of the elastomer of the elastomericmaterial (as evidenced by a sudden drop in the ductility and elasticityof the material) should be less than about 0° C. Preferably, the T_(g)of the elastomer is less than about -40° C., and more preferably is lessthan about -50° C. The elastomer should have an elongation to break ofat least about 50%. Preferably, the elongation to break is at leastabout 100%, and more preferably, it is about 300% for more superiorperformance.

A wide variety of elastomeric materials and formulations may be utilizedin this invention. The essential requirement is that the matrixmaterials of this invention have appropriately low moduli as notedabove. Representative examples of suitable elastomers of the elastomericmaterial have their structures, properties, and formulations togetherwith crosslinking procedures summarized in the Encyclopedia of PolymerScience, Volume 5, "Elastomers-Synthetic" (John Wiley & Sons Inc.,1964). For example, any of the following materials may be employed:polybutadiene, polyisoprene, natural rubber, ethylene-propylenecopolymers, ethylene-propylene-diene terpolymers, polysulfide polymers,polyurethane elastomers, chlorosulfonated polyethylene, polychloroprene,plasticized polyvinylchloride using dioctyl phthalate or otherplasticers well known in the art, butadiene acrylonitrile elastomers,poly(isobutylene-co-isoprene), polyacrylates, polyesters, polyethers,fluoroelastomers, silicone elastomers, thermoplastic elastomers,copolymers of ethylene.

Particularly useful elastomers are block copolymers of conjugated dienesand vinyl aromatic monomers. Butadiene and isoprene are preferredconjugated diene elastomers. Styrene, vinyl toluene and t-butyl styreneare preferred conjugated aromatic monomers. Block copolymersincorporating polyisoprene may be hydrogenated to produce thermoplasticelastomers having saturated hydrocarbon elastomer segments. The polymersmay be simple tri-block copolymers of the type A--B--A, multi-blockcopolymers of the type (AB)_(n) (n=2-10) or radial configurationcopolymers of the type R--(BA)_(x) (x=3-150); wherein A is a block froma polyvinyl aromatic monomer and B is a block from a conjugated dieneelastomer. Many of these polymers are produced commercially by the ShellChemical Co. and described in the bulletin "Kraton ThermoplasticRubber", SC-68-81.

Most preferably, the elastomeric material consists essentially of one ormore of the above noted elastomers. The low modulus elastomeric materialmay also include fillers such as carbon black, silica, glassmicroballoons, etc. up to an amount not to exceed about 300% by weightof elastomer, preferably not to exceed about 100% by weight, and may beextended with oils and vulcanized by sulfur, peroxide, metal oxide, orradiation cure systems using methods well known to rubber technologistsof ordinary skill. Blends of different elastomeric materials may be usedtogether or one or more elastomeric materials may be blended with one ormore thermoplastics. High density, low density, and linear low densitypolethylene may be cross-linked to obtain a material of appropriateproperties, either alone or as blends. In every instance, the modulus ofthe elastomeric material should not exceed about 6000 psi (41,400 kPa),preferably is less than about 5,000 psi (31,500 kPa), and mostpreferably is less than about 2500 psi (17,250 kPa).

The proportion of coating on the coated fibers or fabrics may vary fromrelatively small amounts (e.g. 1% by weight of fibers) to relativelylarge amounts (e.g. 150% by weight of fibers), depending upon whetherthe coating material has any impact or ballistic-resistant properties ofits own (which is generally not the case) and upon the rigidity, shape,heat resistance, wear resistance, flammability resistance and otherproperties desired for the complex composite article. In general,ballistic-resistant articles of the present invention containing coatedfibers should have a relatively minor proportion of coating (e.g., about10-30 percent by weight of fibers), since the ballistic-resistantproperties are almost entirely attributable to the fiber. Nevertheless,coated fibers with higher coating contents may be employed. Generally,however, when the coating constitutes greater than about 60% (by weightof fiber), the coated fiber is consolidated with similar coated fibersto form a simple composite without the use of additional matrixmaterial.

The coating may be applied to the fiber in a variety of ways. One methodis to apply the resin of the coating material to the stretched highmodulus fibers either as a liquid, a sticky solid or particles insuspension, or as a fluidized bed. Alternatively, the coating may beapplied as a solution or emulsion in a suitable solvent which does notadversely affect the properties of the fiber at the temperature ofapplication. While any liquid capable of dissolving or dispersing thecoating polymer may be used, preferred groups of solvents include water,paraffin oils, ketones, alcohols, aromatic solvents or hydrocarbonsolvents or mixtures thereof, with illustrative specific solventsincluding paraffin oil, xylene, toluene and octane. The techniques usedto dissolve or disperse the coating polymers in the solvents will bethose conventionally used for the coating of similar elastomericmaterials on a variety of substrates.

Other techniques for applying the coating to the fibers may be used,including coating of the high modulus precursor (gel fiber) before thehigh temperature stretching operation, either before or after removal ofthe solvent from the fiber. The fiber may then be stretched at elevatedtemperatures to produce the coated fibers. The gel fiber may be passedthrough a solution of the appropriate coating polymer (solvent may beparaffin oil, aromatic or aliphatic solvent) under conditions to attainthe desired coating. Crystallization of the high molecular weightpolyethylene in the gel fiber may or may not have taken place before thefiber passes into the cooling solution. Alternatively, the fiber may beextruded into a fluidized bed of the appropriate polymeric powder.

Furthermore, if the fiber achieves its final properties only after astretching operation or other manipulative process, e.g. solventexchanging, drying or the like, it is contemplated that the coating maybe applied to a precursor material of the final fiber. In such cases,the desired and preferred tenacity, modulus and other properties of thefiber should be judged by continuing the manipulative process on thefiber precursor in a manner corresponding to that employed on the coatedfiber precursor. Thus, for example, if the coating is applied to thexerogel fiber described in U.S. application Ser. No. 572,607 of Kaveshet al., and the coated xerogel fiber is then stretched under definedtemperature and stretch ratio conditions, then the fiber tenacity andfiber modulus values would be measured on uncoated xerogel fiber whichis similarly stretched.

It has also been discovered that coated fiber in which the aspect ratio(ratio of fiber width to thickness) is at least about 5, unexpectedlycan be even more effective than coated-fiber forms (e.g., yarn,generally of a circular cross section) when producingballistic-resistant composites. In particular embodiments of theinvention, the aspect ratio of the strip is at least 50, more preferablyis at least 100 and most preferably is at least 150. Surprisingly, eventhough ECPE strip generally has significantly lower tensile propertiesthan an ECPE yarn material produced under equivalent process conditions(generally produced from fibers having an aspect ratio of approximately1), the ballistic resistance of the composite constructed from ≧5 aspectratio ECPE fiber is much higher than the ballistic resistance of acomposite constructed from ECPE yarns.

It is a critical aspect of the invention that each fiber must besubstantially coated with a low modulus elastomeric material for theproduction of composites having improved impact protection. Moreover, itis a critical aspect of the invention that each filament of each fibermust be substantially coated with the low modulus elastomeric materialto produce composites having maximum ballistic resistance. A fiber orfilament is substantially coated by using any of the coating processesdescribed above or can be substantially coated by employing any otherprocess capable of producing a fiber or filament coated essentially tothe same degree as a fiber or filament coated by the processes describedheretofore (e.g., by employing known high pressure molding techniques).

The fibers and networks produced therefrom are formed into simplecomposite materials as the precursor to preparing the complex compositearticles of the present invention. The term, simple composite, isintended to mean combinations of fiber or fabric with a single majormatrix material, which may include minor proportions of other materialssuch as fillers, lubricants or the like as noted heretofore.

When coated fibers and networks produced therefrom are employed,suitable matrix materials include polyethylenes, cross-linkedpolyethylenes, polypropylenes, ethylene copolymers, propylene copolymersand other olefin polymers and copolymers. Examples of such other matrixmaterials include unsaturated polyesters, phenolics, polybutyrals, epoxyresins and polyurethane resins and other low modulus resins curablebelow the melting point of the fiber.

When uncoated fibers and networks produced therefrom are employed, thelow modulus elastomeric materials discussed above are used as thecoatings for each of the individual filaments of the fiber (or thenetwork) and as matrix materials to provide a composite havingsignificantly improved impact resistance. As noted above for theelastomeric material, the elastomeric matrix material, which comprisesan elastomer, has a tensile modulus, measured at about 23° C., of lessthan about 6,000 psi (41,400 kPa). Preferably, the tensile modulus ofthe elastomeric matrix material is less than about 5,000 psi (34,500kPa), and more preferably is less than about 2,500 psi (17,250 kPa) toprovide even more improved performance. Similarly, the glass transitiontemperature (T_(g)) of the elastomer of the elastomeric matrix material(as evidenced by a sudden drop in the ductility and elasticity of thematerial) should be less than about 0° C. Preferably, the T_(g) of theelastomer is less than about -40° C., and more preferably is less thanabout -50° C. The elastomer should have an elongation to break of atleast about 50%. Preferably, the elongation to break is at least about100%, and more preferably, it is about 300% for more superiorperformance.

The proportion of elastomeric matrix material to fiber is variable forthe simple composites, with matrix material amounts of from about 5% toabout 150%, by weight of fibers, representing the broad general range.Within this range, it is preferred to use composites having a relativelyhigh fiber content, such as composites having only 10-50% matrixmaterial, by weight of fibers, and more preferably 10-30% matrixmaterial.

Stated another way, the fiber network occupies different proportions ofthe total volume of the simple composite. Preferably, however, the fibernetwork comprises at least about 30 volume percent of the simplecomposite. For ballistic protecting, the fiber network comprises atleast about 50 volume percent, more preferably between about 70 volumepercent, and most preferably at least about 75 volume percent, with thematrix occupying the remaining volume.

A particularly effective technique for preparing a preferred, simplecomposite prepreg comprised of substantially parallel, unidirectionallyaligned fibers includes the steps of pulling a fiber through a bathcontaining a solution of an elastomer matrix, and helically winding thisfiber into a single sheet-like layer around and along the length of asuitable form, such as a cylinder. The solvent is then evaporatedleaving a prepreg sheet of fiber embedded in a matrix that can beremoved from the cylindrical form. Alternatively, a plurality of fiberscan be simultaneously pulled through the bath of elastomer solution andlaid down in closely positioned, substantially parallel relation to oneanother on a suitable surface. Evaporation of the solvent leaves aprepreg sheet comprised of elastomer coated fibers which aresubstantially parallel and aligned along a common fiber direction. Thesheet is suitable for subsequent processing such as laminating toanother sheet.

Similarly, a yarn-type simple composite can be produced by pulling agroup of filaments through the solution of elastomeric material tosubstantially coat each of the individual filaments, and thenevaporating the solvent to form the coated yarn. The yarn can then, forexample, be employed to form fabrics, which in turn, can be used to formdesired complex composite structures. Moreover, the coated yarn can alsobe processed into a simple composite by employing conventional filamentwinding techniques; for example, the simple composite can have coatedyarn formed wound into overlapping fiber layers.

Simple composite materials may be constructed and arranged in a varietyof forms. It is convenient to characterize the geometries of suchcomposites by the geometries of the fibers and then to indicate that thematrix material may occupy part or all of the void space left by thenetwork of fibers. One such suitable arrangement is a plurality oflayers or laminates in which the coated fibers are arranged in asheet-like array and aligned parallel to one another along a commonfiber direction. Successive layers of such coated, undirectional fiberscan be rotated with respect to the previous layer. An example of suchlaminate structures are composites with the second, third, fourth andfifth layers rotated +45°, -45°, 90° and 0°, with respect to the firstlayer, but not necessarily in that order. Other examples includecomposites with alternating layers rotated 90° with respect to eachother.

One technique for forming a laminate includes the steps of arrangingcoated fibers into a desired network structure, and then consolidatingand heat setting the overall structure to cause the coating material toflow and occupy the remaining void spaces, thus producing a continuousmatrice. Another technique is to arrange layers or other structures ofcoated or uncoated fiber adjacent to and between various forms, e.g.films, of the matrix material and then to consolidate and heat set theoverall structure. In the above cases, it is possible that the matrixcan be caused to stick or flow without completely melting. In general,if the matrix material is caused to melt, relatively little pressure isrequired to form the composite; while if the matrix material is onlyheated to a sticking point, generally more pressure is required. Also,the pressure and time to set the composite and to achieve optimalproperties will generally depend on the nature of the matrix material(chemical composition as well as molecular weight) and processingtemperature.

The simple elastomeric matrix composites are incorporated into complexcomposites to provide a rigid complex composite article suitable, forexample, as structural ballistic-resistant components, such as helmets,structural members of aircraft, and vehicle panels. The term "rigid" asused in the present specification and claims, is intended to includesemi-flexible and semi-rigid structures that are capable of being freestanding, without collapsing. To form the complex composite, at leastone substantially rigid layer is bonded or otherwise connected to amajor surface of the simple composite. The resultant complex compositearticle is capable of standing by itself and is impact resistant. Wherethere is only one layer, the simple composite ordinarily forms a remoteportion of the composite article; that is a portion that is notinitially exposed to the environment, e.g., the impact of an oncomingprojectile. Where there is more than one layer, the simple composite mayform, for example, a core portion that is sandwiched between two rigidlayers, as is particularly useful, for example, in helmet applications.Other forms of the complex composite are also suitable, for example acomposite comprising multiple alternating layers of simple composite andrigid layer.

The rigid layers are preferably comprised of an impact resistantmaterial, such as steel plate, composite armor plate, ceramic reinforcedmetallic composite, ceramic plate, concrete, and high strength fibercomposites (for example, an aramid fiber and a high modulus, resinmatrix such as epoxy or phenolic resin vinyl ester, unsaturatedpolyester, thermoplastics, Nylon® 6, nylon 6, 6 and polyvinylidinehalides.) Most preferably, the rigid impact resistant layer is one whichis ballistically effective, such as ceramic plates or ceramic reinforcedmetal composites. A desirable embodiment of our invention is the use ofa rigid impact resistant layer which will at least partially deform theinitial impact surface of the projectile or cause the projectile toshatter such as aluminum oxide, boron carbide, silicon carbide andberyllium oxide (see Laible, supra, Chapters 5-7 for additional usefulrigid layers). For example, a particularly useful ballistic resistantcomplex composite comprises a simple composite comprisinghighly-oriented ultra-high molecular weight polyethylene fiber in anelastomeric matrix on which is formed at least one layer comprisinghighly-orientated ultra-high molecular weight polyethylene fiber in arigid matrix, such as an epoxy resin. Other suitable materials for theface sheets include materials which may be heat resistant, flameresistant, solvent resistant, radiation resistant, or combinationsthereof such as stainless steel, copper, aluminum oxides, titanium, etc.

As a portion of the rigid impact resistant composite, the volume percentof the simple composite is variable depending upon the desiredproperties of the final product. The volume percent of the simplecomposite to the complex composite is ordinarily at least about 10%,preferably at least about 30%, and most preferably at least about 60%(for maximizing ballistic resistance). The volume percent of the simplecomposite to the complex composite is ordinarily at least about 10%,preferably at least about 30%, and most preferably at least about 60%(for maximizing ballistic resistance). The examples illustrate theeffectiveness of a simple composite in a complex structure at variouspercentages of the simple composite to the total. For example, variouscompromises between structural rigidity and ballistic performance areattainable depending upon the specific material choices and the relativeproperties of the simple composites and rigid layers.

Studies of ballistic composites employ a 22 caliber, non-deforming steelfragment of specified weight, hardness and dimensions (Mil-Spec.MIL-P-46593A(ORD)). The protective power of a structure is normallyexpressed by citing the impacting velocity at which 50% of theprojectiles are stopped, and is designated the V₅₀ value.

Usually, a composite armor has the geometrical shape of a shell orplate. The specific weight of the shells and plates can be expressed interms of the areal density. This areal density corresponds to the weightper unit area of the structure. In the case of fiber reinforcedcomposites, the ballistic resistance of which depends mostly on thefiber, another useful weight characteristic is the fiber areal densityof composites. This term corresponds to the weight of the fiberreinforcement per unit area of the composite.

The following examples are presented to provide a more completeunderstanding of the invention. The specific techniques, conditions,materials, proportions and reported data set forth to illustrate theprinciples of the invention are exemplary and should not be construed aslimiting the scope of the invention.

EXAMPLE 1

A ballistic target was prepared by consolidation of a plurality ofsheets comprised of unidirectional, high strength, extended chainpolyethylene (ECPE) yarn impregnated with a thermoplastic elastomermatrix. The target was produced from yarn, Yarn 1, processed inaccordance with Precursor Preparation Method 1 and Molding Procedure 1.

Yarn 1: This yarn had a yarn tenacity of approximately 29.5 g/denier, amodulus of approximately 1250 g/denier, an energy-to-break ofapproximately 55 Joules/g, a yarn denier of approximately 1200 and anindividual filament denier of approximately 10 (118 filament, untwistedyarn).

Precursor Preparation Method 1: Yarn 1 was pulled simultaneously fromtwo spools and the two yarn strands passed around a smooth guideimmersed in a beaker that contained a solution of thermoplasticelastomer in a volatile solvent. The coated yarns were helically wrappedin a closely positioned, side-by-side arrangement around a one footdiameter rotating drum while the immersed roller and beaker weretraversed along the length of the drum. After traversing the length ofthe drum and the two strands of yarn were cut and the drum was rotateduntil the solvent had evaporated. The drum was stopped and the prepregwas cut along the length of the drum and then peeled off to yield asheet having fiber areal density of 0.148 kg/m² and weight % fiber of72.7%. The resultant thin prepreg sheet was comprised of a plurality ofsubstantially parallel strands of coated yarn aligned along a common

The thermoplastic elastomer employed was Kraton D1107, a commercialproduct of the Shell Chemical Company. This elastomer is a triblockcopolymer of the polystyrene-polyisoprene-polystyrene having about 14weight % styrene. The coating solution was comprised of about 70 g ofrubber (elastomer) per litre of dichloromethane solvent.

Molding Procedure 1: In this molding procedure the prepreg was cut intoa plurality of square sheets having sides 30.5 cm (one ft.) in length.These squares were stacked together with the fiber length direction ineach prepreg sheet perpendicular to the fiber length in adjacent sheets.A thin square of aluminum foil was placed over the top and under thebottom of the stacked prepreg sheets. Two Apollo plates (0.05 cm thickchrome coated steel plates) coated with a general purpose mold releasewere used to sandwich the sample after a thermocouple probe was insertedapproximately 2 cm from the corner of the sample between the two middleprepreg sheet layers. This cold assembly was placed between two platensof a hydraulic press and subjected to a temperature of approximately130° C. and a pressure of approximately 552 kPa (80 psi). Five minutesafter the thermocouple indicated a temperature of 120° C., water coolantwas passed through the platen. Pressure was released when the sampletemperature was less than 50° C.

EXAMPLE 2

Two layers of 2X2 basket weave Kevlar® 29 fabric of areal density of0.4515 kg/m² were coated with a general purpose epoxy resin based on thereaction product of Bisphenol A and epichlorohydrin (Epon® 828 resinwith Cure Agent® A, diethylaminopropylamine, in the weight ratio of 100to 6, both of which are commercial products of Shell Chemical Company).The two layers were plied together and molded between two mold releasecoated Apollo plates in a hydraulic press at 60 psi (≈41 kPa) at 105° C.for 90 minutes.

Prepreg sheets were prepared according to Precursor Preparation Method 1and were stacked together in an identical manner to that used in Example1, except that they were laid onto the cured rigid facing. This assemblywas then molded in a similar manner to that used in Example 1 to producea 6 inch (15.2 cm) square ballistic target with a rigid facing on oneside.

EXAMPLE 3

A ballistic target was prepared in a similar manner to Example 2 exceptthat two rigid facings were utilized, each containing high moduluspolyethylene fabric reinforcement. Each facing contained two layers of aplain weave fabric prepared from untwisted Yarn 1.

EXAMPLE 4

Another ballistic target was prepared in an identical manner to that ofExample 2, except that the facing resin was a polyvinylbutyral modifiedphenolic resin supplied by Gentex Corporation.

EXAMPLE 5

Data given in Table 1 compares a simple composite (Example 1) withcomplex composites (Examples 2-4) formed from the simple compositesystem of Example 1. The composites of Examples 2-4 have rigid facingson at least the initial impact side of the complex composite. It shouldbe noted that the simple ballistic composite is more effective thanknown rigid ballistic composites of substantially the same arealdensity.

To compare structures having different V₅₀ values and different arealdensities, this example state the ratios of (a) the kinetic energy(Joules) of the projectile at the V₅₀ velocity, to (b) the areal densityof the fiber or of the composite (kg/m²). These ratios are designated asthe Specific Energy Absorption of fiber (SEA) and Specific EnergyAbsorption of Composite (SEAC), respectively.

                  TABLE 1                                                         ______________________________________                                        Ballistic Performance of A-900 Elastomeric Composites                         With and Without Rigid Facings                                                Example    1       2          3     4                                         ______________________________________                                        CORE                                                                          ECPE Fiber AD                                                                            6.20    5.11       4.74  5.10                                      Total Core AD                                                                            8.53    6.43       5.92  6.60                                      FACINGS                                                                       Number     None    1          2     1                                         Fabric (plain                                                                            None    Kevlar ® 29                                                                          ECPE  Kevlar ® 29                           weave)                                                                        Resin      None    Epoxy      Epoxy Phenolic                                  Fabric AD    0      0.903     1.30   0.903                                    Facing AD    0     1.29       2.07  1.29                                      TOTAL                                                                         COMPOSITE                                                                     FIBER AD   6.20    6.01       6.04  6.00                                      COMPOSITE  8.53    7.72       7.99  7.89                                      AD                                                                            V.sub.50 (ft/sec)                                                                        2151    2078       2118  >2189*                                    SEA        38.2    36.1       38.0  >40.9                                     SEAC       27.8    28.6       28.7  >31.1                                     Overall Wt % of                                                                          72.6    77.8       75.6  76.0                                      ECPE Fiber in                                                                 Core                                                                          Overall Wt % of                                                                          72.6    66.0       59.3  64.5                                      Core ECPE in                                                                  Composite                                                                     ______________________________________                                         Core matrix  Kraton D 1107 thermoplastic elastomer                            AD  areal density in kg/m.sup.2                                               SEA  specific energy absorption in Jm.sup.2 /kg of fiber                      SEAC  specific energy absorption in Jm.sup.2 /kg of composite                 *V.sub.50 not established. Sample was destroyed without a complete            penetration. Calculations were carried out using the highest fragment         velocity tested (a partial penetration).                                 

In each instance, the complex composites are ballistically as or moreeffective than the simple composite. The SEAC, based on total compositeareal densities, is at least as high for each complex composite as forthe simple composite consisting of ECPE fiber in the low modulus,thermoplastic elastomer. Unexpectedly, however, the wt % of core ECPE inthe complex composites is significantly reduced as compared to the coreECPE in the simple composite.

EXAMPLE 6

For comparision purposes, a composite, identical in structure to thefacings of Example 3, was prepared in an identical manner to the facingstherein to produce a composite and fiber areal density of 7.96 and 5.90kg/m², respectively. V₅₀ value was determined in the usual manner andfound to be 1649 ft/sec, corresponding to a SEA of 23.5 Jm² /kg. Fromthis example, it is quite clear that the complex composites of ourinvention are significantly more effective in ballistic applicationsthan simple rigid composites.

EXAMPLE 7

Samples were cut from ballistic resistant composite Example 1 andExample 3. Their flexural rigidity was compared using a three pointflexing test using an Instron testing machine (5 in span, 0.2 in/mincrosshead rate). The ratio of deflection under a loading force, λ, to aloading force, P, λ/P in the initial part of the Instron diagram, andapparent flexural modulus (E_(a)) of each composite are shown in Table2. (Deflection, λ, is measured under the loading force P).

                  TABLE 2                                                         ______________________________________                                                                  Length                                              Ex.  Thickness (in)                                                                           Width (in)                                                                              (in)  λ/P                                                                         E.sub.a (psi)                                                                        SEA                               ______________________________________                                        3    0.39       0.85      6     0.024                                                                              26,000 38.0                              1    0.36       1.08      6     0.2   3,000 38.2                              ______________________________________                                    

The apparent flexural modulus (E_(a)) is calculated using the formula:##EQU1## where L is the sample length, b is the sample width, and h isthe sample thickness. (Although we ignored the contribution of shear, anobjective comparison of the relative rigidities of these samples can bemade taking into account variations in the sample size).

This example shows that a complex composite of our invention (Example 3)having the same composition is about 8.7 times more rigid than a simplecomposite (Example 1) from which it is made, and that it providessimilar ballistic performance at a lower percentage of fiber in the core(simple composite). Also, the SEA of Example 3 of 38.0 Jm² /kg issignificantly greater than the value of 35.0 Jm² /kg calculated from theballistic results obtained for Examples 1 and 5 utilizing the Rule ofMixture.

EXAMPLE 8

Shore Durometer Hardness Type D measurements were taken in accordancewith ASTM Procedure D-2240 for Examples 1-4 and for three simplecomposite samples (A-C employing different matrix materials. ExamplesA-C were produced by procedures described in examples 14, 15, and 17 ofU.S. patent application Ser. No. 691,048, Harpell et al, filed Jan. 14,1985, and commonly assigned (the procedures are summarized in footnotes1-3 in Table 3 hereinbelow). The results of the test (and the SEA ofeach sample) are given in Table 3 below.

                  TABLE 3                                                         ______________________________________                                                       Durometer SEA                                                  Sample         reading   Jm.sup.2 /kg                                         ______________________________________                                        Example 1      40.0      38.2                                                 Example 2      71.5      38.0                                                 Example 3      80.0      36.7                                                 Example 4      76.0      40.9                                                 A.sup.1        38.2      32.0                                                 B.sup.2        63.6      30.4                                                 C.sup.3        71.5      29.9                                                 ______________________________________                                         .sup.1 Sample A was prepared according to Precursor Preparation Method 1      (described above), except the coating consisted of a solution of              polycaprotactone in dichloromethane [53 g. (PCL700, Union Carbide)/ L].       Molding Procedure 1 (described above was used, except LDPE film was           substituted for the aluminum foil and molding occured at 3.5 mPa to a         temperature of 125° C., then doubled to 7 mPa for 5 minutes.           .sup.2 Sample B was prepared according to Precursor Preparation Method 1,     except the coating consisted of a solution of LDPE in toluene (67 g/ L)       held at 80° C. Molding Procedure 1 was employed, except that LDPE      film was substituted for the foil and molding occured using a hydraulic       press at 7.5 mPa (1000 psi) for a time until the molding temperature          reached 125° C., and for 10 minutes thereafter followed by cooling     of the press with water.                                                      .sup.3 Sample C was prepared according to Precursor Preparation Method 1,     except the coating was 400 g Epon 828, 24.3 ml                                diethyleminopropylamine/liter dichloromethane, and a release paper was        used to cover the rotating dram. Molding was carried out as for Sample B,     except the mold temperature was 110° C. for 90 minutes at a            pressure of 7665 kPa (110 psi).                                          

From Table 3, it is apparent that simple composites employingnon-elastomeric matrixes (Samples A-C) exhibit decreased utility asballistic resistant composites with increasing hardness of the matrix.When an elastomeric material is employed to form a simple composite(Example 1), hardness is low but ballistic resistance increasesdramatically. With our invention (Examples 2-4), we are able to providea high degree of hardness while at least maintaining the ballisticperformance associated with the elastomeric matrix simple composite.

EXAMPLE 9

A rigid complex composite consisting of an alumina plate (33.6 kg/m²)backed by a composite of extended chain polyethylene (1200 denier,modulus 1000 g/denier, tenacity≈30 g/denier) in a matrix of Kraton®D1107 (AD_(fiber) =9.10 kg/m², AD_(composite) =13.0 kg/m²) was testedfor ballistic performance against 30 caliber armor piercing rounds (164grains). For comparison purposes, a second rigid complex compositeconsisting of an alumina plate (33.6 kg/m²) backed by a composite ofKevlar® 29 fabric in Dow Derakane® 8086 resin (a high impact resistantvinyl ester resin) was similarly tested. The results, reproduced inTable 4 below, clearly show that on an energy absorption basis (SEA),the extended chain polyethylene fiber containing structure was more than1.5 times as ballistically effective against the 30 caliber armorpiercing round as the Kevlar fiber containing structure.

                  TABLE 4                                                         ______________________________________                                        Fiber Reinforced  Total AD                                                    Composite         Ceramic &         SEA                                               AD.sub.f AD.sub.c Composite                                                                             V.sub.50                                                                            (J.m.sup.2 /                          Fiber   (kg/m.sup.2)                                                                           (kg/m.sup.2)                                                                           (kg/m.sup.2)                                                                          ft/sec                                                                              Kg)                                   ______________________________________                                        Kevlar 29                                                                             8.88     13.1     44.7     2632   76.5                                ECPE    9.10     13.0     44.6    >3289 >119.7                                ______________________________________                                    

While we have described our invention in detail, it should be clear thatmodifications, changes, and alternations may be made without departingfrom the scope of the invention as defined by the appended claims.

We claim:
 1. A composite article of manufacture comprising:(a) fiberhaving a tensile modulus of at least about 160 g/denier and a tenacityof at least about 7 g/denier substantially coated with an elastomericmaterial which has a tensile modulus (measured at about 23° C.) of lessthan about 6,000 psi (414 MPa); and (b) at least one rigid materialarranged with said coated fiber to form a rigid composite article.
 2. Anarticle as recited in claim 1 wherein said article comprises a pluralityof said coated fibers.
 3. An article as recited in claim 1 wherein saidfiber comprises a plurality of filaments.
 4. An article as recited inclaim 3 wherein each filament of fiber is substantially coated with saidelastomeric material.
 5. An article as recited in claim 2 furthercomprising an elastomeric matrix material which has a tensile modulus(measured at about 23° C.) of less than about 6,000 psi (414 mPa)combined with said coated fibers to form a simple composite.
 6. Anarticle as recited in claim 5 wherein said elastomeric matrix materialand said elastomeric material are the same material.
 7. An article asrecited in claim 2 further comprising a matrix material combined withsaid coated fibers to form a simple composite.
 8. An article as recitedin claim 5 wherein said at least one rigid material is arranged as alayer on a major surface of said simple composite.
 9. An article asrecited in claim 7 wherein said at least one rigid material is arrangedas a layer on a major surface of said simple composite.
 10. An articleas recited in claim 1 wherein said article comprises a sheet-like arrayof a plurality of said fiber.
 11. An article as recited in claim 1wherein said article comprises a plurality of said fiber in a non-wovenbut regular pattern.
 12. An article as recited in claim 5 wherein thevolume fraction of fiber in said simple composite is at least about 0.3.13. An article as recited in claim 5 wherein the volume fraction of saidfiber in said simple composite is at least about 0.5.
 14. An article asrecited in claim 5 wherein the volume fraction of fiber in said simplecomposite is at least about 0.75.
 15. An article as recited in claim 1wherein said elastomeric matrix material comprises an elastomer having aglass transition temperature of less than about 0° C.
 16. An article asrecited in claim 15 wherein said elastomer has a glass transitiontemperature of less than about -40° C.
 17. An article as recited inclaim 15 wherein said elastomer has tensile modulus of less than about15,000 psi.
 18. An article as recited in claim 1 wherein saidelastomeric material has a tensile modulus of less than about 2500 psi.19. An article as recited in claim 1 wherein said fiber is highmolecular weight fiber having a tensile modulus of at least about 500g/denier and a tenacity of at least about 15 g/denier.
 20. An article asrecited in claim 1 wherein said fiber is selected from the groupconsisting of: polypropylene fiber having a weight average molecularweight of at least about 750,000, a modulus of at least about 200g/denier and a tenacity of at least about 11 g/denier; polyethylenefiber having a weight average molecular weight of at least about500,000, a modulus of at least about 500 g/denier and a tenacity of atleast about 15 g/denier; aramid fiber having a modulus of at least about500 g/denier and a tenacity of at least about 18 g/denier, highmolecular weight polyvinyl alcohol fiber having a weight averagemolecular weight of at least about 750,000, a modulus of at least about200 g/denier and a tenacity of at least about 10 g/denier; and,combinations thereof.
 21. An article as recited in claim 5 wherein saidsimple composite is a sheet material to which is laminated at least oneadditional simple composite sheet material.
 22. An article as recited inclaim 1 comprising a plurality of said fiber arranged as yarn.
 23. Anarticle as recited in claim 22 wherein the yarn is arranged to form afabric.
 24. An article as recited in claim 5 wherein said fiber isarranged to form a woven fabric.
 25. An article as recited in claim 1wherein a plurality of fiber are arranged in a matrix of said elastomermaterial to form a sheet-like material on which at least two rigidmaterials in the form of layers are provided, at least one rigid layerbeing provided on each side of said sheet-like material.
 26. A ballisticresistant composite article of manufacture comprising:(a) fiber having atensile modulus of at least about 200 g/denier and a tenacity of atleast about 10 g/denier substantially coated with an elastomericmaterial which has a tensile modulus (measured at about 23° C.) of lessthan about 6,000 psi (414 MPa); and (b) at least one rigid materialarranged with said coated fiber to form a rigid composite article. 27.An article as recited in claim 26, wherein said fiber is high molecularweight fiber having a tensile modulus of at least about 500 g/denier anda tenacity of at least about 15 g/denier.
 28. An article as recited inclaim 26 comprising a plurality of said fiber arranged as a sheet-likearray.
 29. An article as recited in claim 26 wherein the volume fractionof fiber in said coated fiber is at least about 0.5.
 30. An article asrecited in claim 26 wherein said elastomeric material comprises anelastomer having a glass transition temperature of less than about -40°C.
 31. An article as recited in claim 26 wherein said elastomericmaterial has a tensile modulus of less than about 2500 psi.
 32. Anarticle as recited in claim 19 wherein said fiber is selected from thegroup consisting of polypropylene fiber having a weight averagemolecular weight of at least about 750,000, polyethylene fiber having amolecular weight of at least about 500,000 and a tenacity of at leastabout 15 g/denier, aramid fiber having a modulus of at least about 500g/denier and a tenacity of at least about 18 g/denier, high molecularweight polyvinyl alcohol fibers having a weight average molecular weightof at least about 750,000, and combinations thereof.
 33. An article asrecited in claim 27 wherein said at least one rigid material compriseshighly oriented ultra-high molecular weight polyethylene fiber in arigid matrix material.
 34. Armor plate comprising the ballisticresistant article of claim
 32. 35. A helmet comprising the ballisticresistant article of claim
 32. 36. A complex composite comprising:(a) asimple composite comprising fibers having a modulus of at least about500 g/denier and a tenacity of at least about 15 g/denier in anelastomeric matrix having a tensile modulus of less than about 6000 psi;and (b) a rigid material comprising a ceramic arranged adjacent saidsimple composite.